a. Field of the Invention
The present invention is directed to systems and methods for mapping and ablating body tissue of the interior regions of the heart for treating cardiac arrhythmias.
b. Description of the Prior Art
Atrial fibrillation (AF) is a common cardiac arrhythmia associated with significant morbidity and mortality. A number of clinical conditions may arise from irregular cardiac functions and the resulting hemodynamic abnormalities associated with AF, including stroke, heart failure and other thromboembolic events. AF is a significant cause of cerebral stroke, wherein the fibrillating motion in the left atrium induces the formation of thrombus. A thromboembolism is subsequently dislodged into the left ventricle and enters the cerebral circulation where stroke may result.
For many years, the only curative treatment for AF has been surgical, with extensive atrial incisions used to compartmentalize the atrial mass below that critical for perpetuating AF. Recently, transcatheter linear radiofrequency ablation in the right or left atrium has been used to replicate surgical procedures in patients with paroxysmal or chronic AF. Such ablation is carried out by a catheter system that performs both mapping and ablation. With current techniques, there is still uncertainty regarding the number of lesions, the optimum ablation site, and the need for continuous lines. As a result, focal ablation has been proposed as an alternative approach, due to the belief that ectopic beats originating within or at the ostium of the pulmonary veins (PV) may be the source of paroxysmal and even persistent AF. Although successful, the technical feasibility of this technique is restricted by the difficulty in mapping the focus if the patient is in AF or has no consistent firing, the frequent existence of multiple foci causing high recurrence rates, and a high incidence of PV stenosis.
There are a number of drawbacks associated with the catheter-based mapping and ablation systems that are currently known in the art. One serious drawback lies in the unstable positioning of the catheter inside the atrium of the heart. When a catheter is not properly stabilized, the mapping becomes difficult and inaccurate.
Another drawback is associated with certain catheter-based systems that utilize an expandable balloon that is inflated to conform to the pulmonary vein ostium. After the balloon is inflated and the catheter positioned, it becomes difficult to map or record the distal PV potentials without removing this catheter and placing another mapping catheter inside the PV. Moreover, inflation of the balloon to conform to the pulmonary vein ostium blocks blood flow to the left atrium, and such prolonged blockage can have adverse effects to the patient. Blockage of blood flow from the PV deprives the patient from receiving oxygenated blood. In addition, the blockage may be a potential source for stenosis.
Thus, there still remains a need for a catheter-based system and method that can effectively map and ablate potentials (also known as spikes) inside PVs which can induce paroxysmal AF, while avoiding the drawbacks set forth above.